Espinosa said the killers must be held accountable, adding that “we cannot tolerate hatred. The fundamental right of religious freedom must be respected everywhere”.

Also reacting, the UN Resident Coordinator in Burkina Faso, Mrs Metsi Makhetha, tweeted her condemnation of the “heinous attacks”.

She offered her condolences to the families of those who lost their lives.

The UN said the attacks occurred just days after its humanitarian officials, including Makhetha, warned of an “unprecedented” rise in “sophisticated armed attacks in the Sahel”.

In a report to member states on Wednesday, the UN Office for the Coordination of Humanitarian Affairs (OCHA), said the development was putting the future of a “whole generation” at stake.

“Violence is spreading in Mali and Niger, as well as Burkina Faso, and risks spilling over into other West African countries.

“This has led to a five-fold rise in the displacement of the local population in the last 12 months, who have seen more than 330,000 people leave their homes, in addition to 100,000 refugees,” OCHA said.